Earthquakes, volcanoes, mountain building, ice ages, landslides, floods, life evolution, plate motions—all of these phenomena have interacted over the vast expanses of deep time to sculpt the dynamic planet that we live on today. Planet Earth presents an overview of several aspects of our home, from a geological perspective. We begin with earthquakes—what they are, what causes them, what effects they have, and what we can do about them. We will emphasize that plate tectonics—the grand unifying theory of geology—explains how the map of our planet's surface has changed radically over geologic time, and why present-day geologic activity—including a variety of devastating natural disasters such as earthquakes—occur where they do. We consider volcanoes, types of eruptions, and typical rocks found there. Finally, we will delve into the processes that produce the energy and mineral resources that modern society depends on, to help understand the context of the environment and sustainability challenges that we will face in the future.

From the lesson

Week 2: Plate Tectonics

In the early twentieth century, publication of the hypothesis on continental drift caused an uproar that soon died down. Data collected in mid-century led geologists to reconsider the idea that continents could move. During the 1960s and 1970s, old ideas were reworked into what is now called the theory of plate tectonics. As we will see, this robust theory encompasses many geological phenomena that appear to be unrelated at first glance: earthquakes and volcanoes, but also ice ages, fossils, and mountains. Today, plate tectonics provides an overarching framework for interpreting the Earth. We study its details in Week 2, but we will return to this theory again and again throughout the rest of this course.